Strongly Removal Mechanism Study Of Fe And Mn In Acid Mine Drainage By Iron And Manganese Oxidizing Bacteria

Acid mine drainage(AMD),which is characterized with low p H,high concentrations of heavy metal,high content of sulfate has posed severely threatening to the safety of ecological environment and human health.There were many methods focused on AMD remediation.However,it was lack of both efficient and environmental friendly technology,especially in AMD with high Fe and Mn concentrations.This paper was relied on National Key Research and Development Plan”Integrated Demonstration and Transformation Model of advanced Treatment and Safe Utilization Technology of Heavy metal Wastewater(No.2016YFC0403000).”The aim of this paper was to explore a microbiology method to deal with the AMD with Fe and Mn contents.In this study,a bacterial consortium for efficient decontamination of high-concentration Fe–Mn acid mine drainage(AMD)was successfully isolated,and the removal mechanism was investigated by high-throughput sequencing and sediment characterizing analysis.After that,the culture conditions of bacteria consortium and the running parameters of the flow column were optimized.The main conclusions of this study were as follows:(1)In the sediments of Qibaoshan mine,the concentrations of heavy metals were all exceeded the standard,especially Fe and Mn contents in the sulfur mine,in which Fe was 76000 mg/Kg and Mn was 1070 mg/Kg.The high through-out sequencing showed that a significant difference in bacterial communities between the mine area and watershed area.The key driving factor for bacterial communities in the watershed were chemical properties,while in mining areas the bacterial community were more affected by heavy metals.Moreover,the study demonstrated that Phyllobacterium,Bacteroides,and Sulfurovum were potentially useful bacterial species for environmental protection.(2)Six manganese oxidizing bacteria were isolated from AMD,three of them were identified to be Bacillus,and the others were belonged to Cupriavidus metallidurans,Ralstonia sp.and Sphingobium sp.,respectively.The biological manganese removal experiments demonstrated that the manganese oxidizing bacteria isolated from mining area could be used as potential bacteria for manganese remediation.(3)A bacterial consortium for efficient decontamination of high-concentration Fe–Mn acid mine drainage(AMD)was successfully isolated from AMD.After acclimated by by serial sub-culturing,the Fe and Mn oxidizing bacterial consortium could survive in the p H range of 4-8,temperature range of 20-30°C.The maximum tolerable concentration of Fe for the acclimated bacteria was 1100 mg/L,and Mn was500 mg/L.The optimal removal conditions of Fe and Mn were obtained by response surface methodology(RSM),for which the p H value was 6.5,temperature was 30°C and the inoculum size was 3.5%.Under the optimized oxidation conditions,the Fe removal ratio was 100%,and the Mn removal ratios increased to 99.8%.(4)The batch experiments confirmed that the Fe and Mn oxidizing bacterial consortium could induce p H rising,which was benefit for bacteria survive and Fe and Mn removal.During the treatment Flavobacterium,Brevundimonas,Stenotrophomonans and Thermomonas were dominated genera,indicating that these bacteria might play vital roles in Fe-Mn removal.Moreover,the sediments characterization further illuminated that the main component of the sediment produced by microbial metabolism was biological iron and manganese oxides.The biogenic sediments were amorphous,with a high specific surface area and functional groups that favored Fe and Mn adsorption in turn.(5)The column experiments were carried out to verify the removal ability of bacteria in the dynamic study,and the results demonstrated that ceramic particles were the optimum filler media for bacteria immobilization.The optimum operating conditions of filter column were p H 4-6,DO 5-6 mg/L,filtration rate 2.0-2.5 L·h^-1,and backwash cycle of 45 days.After operated 36 days,the biofilter reached saturation,the average removal efficiencies of Fe and Mn were 99.8%and 98.6%,respectively.The meta-genomic sequencing analysis showed that Proteobacteria,Actinobacteria and Gemmatimonadetes were most abundant phylums during the treatment,and Two-Component Signal Transduction System and ABC transport were dominate function groups.(6)The sludge reusing experiment showed that the sludge could be used as biological adsorbent.The maximum adsorption capcity of Mn²⁺was 16.67mg·g^-1when the p H was 7.0,the dosage was 0.2 g/L,and adsorption equilibrium time was 240 min.The adsorption of Mn²⁺on the biological adsorbent could be approximated favorably by pseudo-second-order and Freundlich model,which indicated that the sorption of Mn²⁺was mainly governed by chemical reaction and it was belonged to multilayer adsorption.To sum up,our results demonstrated that acclimated Fe-Mn oxidizing bacteria have potential application in AMD remediation.And the removal of Fe and Mn was not only by bio-oxidation and chemical oxidation but also by the absorption or co-precipitation of biosynthetic Fe-Mn oxides.